2219 References and Notes (1) Ben May Laboratory, University of Chicago, Chicago, Ill. 60637. (2) E. U. Condon, W. Altar, and H. Eyring, J. Chem. Phys., 5, 753 (1937). (3) W. Moffitt, R. B. Woodward, A. Moscowitz, W. Klyne. and C. Djerassi, J. Am. Chem. SOC.,83,4013 (1961). (4) See for a recent review, e.g., ref 10. (5) C. A. Emeis and L. J. Oosterhoff, Chem. Phys. Lett., 1, 129, 268 (1967). (6)W. C. M. C. Kokke and L. J. Oosterhoff, J. Am. Chem. SOC.,94, 7583 (1972). (7) R. F. R. Dezentje and H. P. J. M. Dekkers, to be submitted for publication. (8) 0. E. Weigang, Jr., J. Chem. Phys., 42, 2244 (1965); 43, 3609 (1965); 48, 4332 (1968). (9) W. Moffitt and A. Moscowitz, J. Chem. Phys., 30, 648 (1959). (10) W. Klyne and D. N. Kirk in “Fundamental Aspects and Recent Developments in Optical Rotatory Dispersion and Circular Dichroism”, F. Ciardeili and P. Salvadori. Ed., Heyden. London, 1973. (11) (a) C. A. Emeis and L. J. Oosterhoff. J. Chem. Phys., 54, 4809 (1971); (b) C. A. Emeis, Thesis, Leiden, 1968.
(12) H. P. J. M. Dekkers, Thesis, Leiden, 1975. (13) F. S. Richardson, J. Phys. Chem., 75,2466 (1971). (14) For the moment we neglect the fact that at room temperature a solution of 3-methylcyclopentanone in a hydrocarbon solvent is not conformationally pure, this being a plausible explanation for the o b ~ e r v a t i o n ’ ~ that the magnitude of the CD of a solution of 3-methylcyclopentanone increases upon lowering the temperature. (15) K. M. Wellman. E. Bunnenberg, and C. Djerassi, J. Am. Chem. SOC.,85, 1870 (1963). (16) See for a discussion of the advantages of this definition the appendix in ref 1l a . (17) Definition 28 is also used in theories on the spectral intensities of diatomic molecules, where it is a starting point for the so-called r-centroid approximation.” (18) P. A. Fraser, Can. J. Phys., 32, 515 (1954). (19) isofenchone was discussed earlier. (20) D. J. Caldwell, J. Chem. Phys., 51, 984 (1969); D. J. Caldwell and H. Eyring, “The Theory of Optical Activity”, Wiley-lnterscience, New York, N.Y., 1971. (21) R. J. Buenker and S. D. Peyerimhoff: J. Chem. Phys., 53, 1368 (1970) (22) V. T. Jones and J. B. Coon, J. Mol. Spectrosc., 31, 137 (1969).
Thione Photochemistry. Cycloaddition in a Saturated Alicyclic System ,2 A. H. Lawrence, C. C. Liao, P. de Mayo,* and V. Ramamurthy Contributionfrom the Photochemistry Unit, Department of Chemistry, Uniuersity of Western Ontario, London, Ontario, Canada. Received J u l y 22, 1975
Abstract: Irradiation of adamantanethione ( A 500 nm) gives the dimer, a 1,3-dithietane. In the presence of olefins thietanes are obtained in a regiospecific, nonstereospecific reaction. The regiospecificity is that expected with the formation of the more stable possible biradical intermediate. In one case, that of cu-methylstyrene, support for the intermediacy of the biradical comes from the isolation of an “ene” product and proof that the latter is formed by intramolecular hydrogen transfer. It is shown that the reactive state of the thione is 3 ( n , ~ * and ) that a,,, 1. Rate constants for dimerization and the addition to ethyl vinyl ether and acrylonitrile have been obtained, and the inefficiency in dimerization and cycloaddition (@ shown to be due to reversion in an intermediate or intermediates to regenerate starting material, and not to a slow reaction. In the case of dimerization, trapping of the thione triplet by thione is diffusion controlled. The mechanism of addition is discussed and the intervention of complexes suggested.
-
-
After a long lapse of time, interest has begun to be drawn Results toward the photochemistry of the thione grouping. While A d a m a n t a n e t h i ~ n e , ’a~ typical saturated thione, shows studies in carbonyl photochemistry were initiated a t the four bands in the absorption spectrum between 200 and 500 turn of the century and continue with vigor unabated, siminm. These are, in increasing energy, SO T I , SO SI lar thione studies date only from the past d e ~ a d e . ~With -I~ (n,r*), SO SZ, SO S3 (r,r*, n,u*).20 No fluorescence the exception of a single report on the reduction of adamanhas been detected and the SI and Sz energies can only be tanethione14 all mechanistic studies have been concerned approximated from the absorption spectrum. Values (nonwith aromatic compounds. In fact, when the present work polar solvent) of near 56 and 95 kcal/mol seem probable. was initiatedI5 there were no reports of the photochemical The triplet energy, based on the emission from a glassy mabehavior of a normal saturated thione, and the position has, trix at 77 KZoa and from the absorption spectrum, is near essentially, remained unchanged.I6 5 2.6 kcal /mol. One of the interesting features that has emerged in the study of aromatic thiones is that they have, under certain Reactions and Products circumstances, the capacity to react from both higher and (a) Photodimerization. Irradiation of 1 in benzene, X lower excited states, and evidence for this has been forth>420 nm, gave the dimer, 2 (Scheme I). The structure of coming from reactions as diverse as reduction, cycloaddi~ ~ behavior ~ ~ ’ ~ ~ may ~ ~ ~well, ~ ~ ~ ’ ~the latter followed from the molecular weight (358 by ostion, and c y ~ l i z a t i o n . ~ ~This mometry, molecular ion 332, and strong accompanying in part, be attributed to the longer lifetime of the S2 state which is, itself, partly a consequence of the large s1-S~enpeak a t 166). the N M R spectrum, and its conversion to adergy separation.18 The separation in aliphatic thiones is amantane by Raney nickel reduction. It was identical in all rather similar, and it is the purpose of this and a following respects with material made by Greidanus by the acid treatment of the thione. The photochemical reaction could be paper in this series to show that a like situation obtains in the photochemistry of a typical alicyclic thione, adamansensitized with benzophenone. tanethione ( 1 ) . In the present paper we record the first cy(b) Cycloaddition to 1,l-Diphenylethylene, Ethyl Vinyl cloaddition reactions of an alicyclic thione and present a deEther (E), and Acrylonitrile (A). A benzene solution of 1 in tailed study of the consequences of excitation into the n , r * the presence of the olefins named gave a single product tostate; in that to follow we will describe the different consegether with the dimer 2. These were shown to have the gross quences of excitation into the S2 state. structure 3, 4, and 5 from their composition and spectro-
-
- -
-
’’
Lawrence, Liao, de Mayo, Ramamurthy
/
Thione Photochemistry
2220 Scheme I
5% R = H ,R = C N
3b,R = R’= C,,H, 4b. R = H, R = OEt 5b. R = H ,R’=CN
R /JR
6,R=CN 7,R = C,,H, Scheme I1
10
12
11
15
14 scopic properties (Experimental Section). The disposition of the substituents was deduced from their mass spectra. Thus, in the case of diphenylethylene the presence of a strong peak at 320 ( M - CH2S) and the absence of any peak a t m/e 148 ( M - CPh2S) indicated the structure 3a rather than 3b. The absence of the latter peak from the mass spectra of 4 and 5, and the presence of peaks a t m/e 192 and 173, respectively, indicated 4a and 5a, as against 4b and 5b.2’ (c) Cycloaddition to Fumaronitrile and trsnsStilbene. Irradiation of the thione in benzene solution with fumaronitrile or trans-stilbene gave, in both cases, two isomeric thietanes. The gross structures followed from analytical and spectroscopic data, but configurational assignments were not made. The adducts 6 from fumaronitrile were formed in approximately equal amounts, those from stilbene in the ratio of 15: I . The adducts 6 both showed AB patterns for the vicinal thietane protons with coupling constants of 9 and Journal of the American Chemical Society
5 Hz, but this appeared insufficient evidence for a stereochemical a s ~ i g n m e n t . ~ - * ~ The recovered olefin was, in both cases, isomerized, the cis/trans ratio being 1:2.7 and 8.3:l for the nitrile and stilbene, respectively. The energy of the nitrile is insufficiently low for efficient energy transfer, and the precise mechanism of isomerization is unknown; it may well be related to mechanism of cycloaddition (see below). Energy transfer from the thione to stilbene (trans-stilbene, ET = 50 kcal/ mol; cis-stilbene, ET = 57 kcal/mol) is possible, and it was found that with 0.02 M thione the &/trans ratio did not vary with the stilbene concentration over the concentration range 0.06-0.4 M. Coincidental or not, the equilibrium reached is approximately that predicted for the triplet-sensitized isomerization.24 (d) Addition to a-Methylstyrene. Two products of addition were isolated: the thietane 8 and 2-adamantyl 2’-phenylallyl sulfide (9)(Scheme 11). The structure of 8 followed
/ 98:8 / April 14, I976
222 1 Table I.
Table 111. Quenching Parameters
Quantum Yields" in Various Solvents at 500 nm and 25O
~
Dielectric constant of (x104)* ( ~ 1 0 ~( )~ ~1 0 ~ ) ~ solvent @dim
Solvent Hexane Cyclohexane Benzene Acetonitrile Methanol
@E
@A
1.6
2.4 1.5 1.2
9.0 7.4
1.1
4.4 3.8 2.2 4.5
I .89 2.02 2.28 38.8 32.63
Average of three runs; error f10%. [ l ] = 0.2 M. [ l ] = 0.1 M; [E] = 2 M. [ l ] = 0.2 M; [A] = 3.04 M. Table 11. Sensitized and Direct Quantum Yields" Mode of excitation
@dim
Direct ( A 500 nm) Sens @-acetonaphthone/ (A 334 nm) Sens @-acetonaphthone/ ( A 306 nm) Sens triphenylend ( A 306 nm) Sens Michler's ketone/ ( A 362 nm)
(xio4)
1.55*
1.7b
s-I
~~~~
x
7.C
s-' x
System"
Slope ( k q ) ?M-'
IO9
I 09
Dimerization9-methylanthracene Acrylonitrile9-methylanthracene Ethyl vinyl ether9-methylanthracene Ethyl vinyl etherallo-ocimene Ethyl vinyl ethercyclooctatetraene
10.3 f 0.7
I .o
I .o
I I .6 f 0.8
I .2
I .4
9.1 f 0.8
0.9
I .3
8.0 f 1 . 1
0.5
1.3
2.2 f 0.5
0.2
13
*
@E
(Xi04)d (Xio4)'
4.3 4.3
3.8 3.7
4.8
4.1
See Figures I and 2. Calculated on the assumption k , = 1.0 X M-I s-l. Calculated from the evaluated bimolecular rate constants for reaction ( k z and k s ) . The unimolecular decay rate constant ( k i ) is unimportant at these concentrations. IO'O
@A
1.5' 1 .8r
a Average of three to four determinations in benzene: error f 10%. [ I ] = 0.2 M. ( I ] = 0.01 M. [ l ] = 0.2 M; [E] = 2 M. [ l ] = 0.2 M; [ A ] = 3.04 M.f [Sens] = 0.01 M.
from spectroscopic and analytical data. T h e mass spectrum (peak a t m/e 238; absence of a peak a t m/e 148) indicated the orientation. Raney nickel desulfuration gave the spiran 10 and the styrene derivative 11. All spectroscopic and analytical data were in accord with these assignments. In particular, 10 showed the high-field pattern expected for the cyclopropylmethylene (AB pattern centered at 0.38 and 1.02 ppm, J = S Hz); for details, see the Experimental Section. The structure of 9 followed from the analytical and spectroscopic data, and from independent synthesis. This was achieved by treatment of 2-adamantylthiol (12) with 2-phenallyl bromide in the presence of ethanolic potash. Substitution of a-trideuteriomethylstyrene in the irradiation gave 14 and 15. The positions of the deuterium atoms were unambiguously indicated by the N M R data. Use of a 1 : 1 mixture of a-trideuterio- and a-triprotiomethylstyrene gave a mixture of 9 and 15 only. Mass spectrometric analysis of the mixture revealed a number of peaks, from the mo5 (5.46% lecular ion of undeuterated material ( M ) to M of M). The ratio of the M 1 (m/e 285) to the M peak was 22.0 f 0.5%; that calculated from the distribution of natural abundance isotopes is estimated to be 22.1%. It must therefore be concluded that no molecules containing a single deuterium atom occur in the mixture, and that the transfer of hydrogen from the methyl to adamantyl positions is entirely intramolecular. The ratio of 8 to 9 was 1 .S: 1 , but that of 14 to 15 was 3.0:l( N M R ) .
+
7.h
+
Quantum Yields The dimerization and the photocycloaddition of 1 to acrylonitrile (A) and ethyl vinyl ether (E) were studied in detail. A general survey of solvent effects (Table I) revealed no marked dependence. A comparison was made of the sensitized reaction (with the triplet sensitizers Michler's ketone and P-acetonaphthone) with that induced directly. The results are shown in Table 11. The efficiency of the two routes is comparable. T h e quantum yields of dimerization and cycloaddition to
acrylonitrile were measured in the presence of varying concentrations of 9-methylanthracene ( E T = 41.9 k c a l / m ~ l ~ ~ ) . Cycloaddition to ethyl vinyl ether was quenched with alloocimene (ET = 47 k ~ a l / m o l ~ 9-methylanthracene, ~), and cyclooctatetraene ( E T < 40 kcal/mo12'). All processes were quenched by the triplet quenchers used u p to a t least SO%. Absorbance problems and side reactions prohibited the use of higher quencher concentrations; slopes are given in Table 111. Quantum yields for cycloaddition to the two olefins were measured as a function both of thione and olefin reciprocal concentration (see Figures 1 and 2). The efficiency decreased in both cases with increasing thione concentration and increased with olefin concentration.
Discussion The results presented here show that adamantanethione (1) in an n , r * state is able to undergo two reactions: dimerization to a 1,3-dithietane and cycloaddition to a variety of olefins to give a thietane. In the latter case the same type of product is obtained whether the olefin be substituted with electron-withdrawing or electron-donating groups. No 1,4dithiane was observed, as in the case of thiobenzophenone.6 The formation of 1,3-dithietanes has been observed as a consequence of ground-state reactions (e.g., ref 19) and of photochemical reactions of other types of substances containing the thiocarbonyl function, e.g., thiophosgene.28 The following discussion will present our arguments for the nature of the mechanism and attempt to rationalize our observations, both qualitative and quantitative, the most striking of the latter being the abysmally low quantum yields (ca. for both dimerization and cycloaddition. The Reactive State. In the photochemistry of alkyl ketones it has been established that both I(n,r*) and 3(n,r*) states may cycloadd to olefins possessing electron-releasing substituent^,^^ but only ketone I(n,r*) states with molecules bearing electron-withdrawing groups.30The reactivity of the SI state may be consequence of its longer lifetime than that of aromatic ketones. Adamantanethione does not fluoresce31 ( + f < 3.6 X The value of kf, calculated from the oscillator strength of the absorption band, is -3 X IO4, whence it follows that the upper limit for T ~ is' -1 2 ns. Such a lifetime does not exclude the intervention of '(n,r*) as the reactive state (see, e.g., ref 17a), but the fact that the quantum yields of both dimerization and cycloaddition are essentially the same, whether by direct excitation or sensitization (Table I I ) , suggests very strongly that the triplet of 1 is the reactive species. The sensitizers, Michler's ketone, &acetonaphthone, and triphenylene, have triplet
Lawrence, Liao, de Mayo. Ramamurthy
/ Thione Photochemistry
2222
/
g8 [
Figure 1. Plots of the reciprocal quantum yields for addition to acrylonitrile ( X ) and ethyl vinyl ether (A) against [ I ] : benzene solution, X 500 nm; average of two determinations.
energies higher than that of 1 3 2 and have high intersystem crossing e f f i ~ i e n c i e s .I~t ~would be expected, thus, that energy transfer should be efficient and near diffusion-controlled.34 Back transfer should be unimportant, since it would be endothermic by > 7 kcal/mol and since the thione lifetime under these conditions (vide infra) is very short (-1O-'O s ) . These ~ ~ results also suggest that intersystem crossing in 1 is high and probably close to unity.36 The identification of the triplet of 1 as the reactive species is supported by the quenching experiment^.^' Linear Stern-Volmer plots to @o/@ = 2 indicate that a t least 50% reaction pathway lies via the triplet. The slopes (k,T) of the Stern-Volmer plots a r e given in Table 111. O n the assumption that the diffusion-controlled quenching rate is 1.0 X l o L oM-' s - ' , ~the ~ values of T under these conditions can be evaluated and are listed in Table 111. In the adjacent column are the values of 7 calculated for the appropriate conditions using the evaluated rate constants (vide infra). As can be seen the agreement is acceptable except in the case of the use of cyclooctatetraene, and, this instance aside, we conclude that this implies that the excited species is the same in all reactions, and that it is quenched by allo-ocimene and 9-methylanthracene a t a near-diffusion rate. The reason for the anomalous behavior of cyclooctatetraene is not clear, and conceivably chemical quenching may be involved.' ] The triplet energy of cyclooctatetraene though believed to be low*' does not seem to have been rigorously demonstrated. Kinetics. Our observations may be accommodated by the set of eq 1 to I O ,
I
0
I
31
+Q
[QT' ''
16
I
I
20
Z 3 Q
+1
+ Q -% 3Q + 1 + 1
Mz
+QZ
3 Q
+ 1+ 0
(8) (9) (10)
where Q = quencher and 0 = olefin. M I represents an intermediate or intermediates between the collision complex and the final product, the dimer 2. This may be an excimer, biradical, or both. I n a similar way M2 is intended to designate an intermediate or intermediates in thietane formation. The reversal of the formation of these intermediates ( k - 2 and k-5) is not required by our results. This does not imply that, in a real sense, the reversion does not occur, but merely that k-2 420 nm). Quantum yield measurements ( A 500 i 7.5 nm) ere carried out on a J A S C O C R M - F A spectroirradiator calibrated at 250 nm using ferrioxalate a ~ t i n o m e t r y .Relative ~~ light intensities 250/500 nm were measured with a thermopile. Quenching of 4a by 9-methylanthracene and cyclooctatetraene was carried out in a merry-go-round apparatus" a t 20 "C using a Hanovia 450-W medium-pressure lamp through Corning 3-72 glass filters (>420 nm). All samples
14, I976
2225 were degassed (residual pressure 420 nm) until disappearance of the thione. Chromatography of the product over silica gel ( B D H 60-200 mesh) gave the dimer 2 which was recrystallized twice from dioxane (mp 305-306', yield 72%). A mixture of the dimer 2 (200 mg, 0.6 mmol) and the W-2 catalyst from I O g of nickel alloy was refluxed for 24 h. After filtration and removal of the solvent, the residue was sublimed (25' (0.01 m m H g ) ) to give adamantane (105 mg, 65%, m p 268-269') identical in all respects with an authentic specimen. A solution of benzophenone (91 mg, 0.05 mmol) in benzene (5 ml) containing the thione (83 mg, 0.5 mmol) was degassed and irradiated at 350 nm (Rayonet) for 6 days. The residue was chromatographed on silica gel (eluent, petroleum ether, 60-80') to give the dimer, mp 305-306' (43 mg, 52%). Irradiation of Adamantanethione and a-Methylstyrene. A solution (degassed) of 790 mg of thione and 5.9 g of a-methylstyrene in benzene (25 ml) was irradiated until disappearance of the thione. Chromatography of the product over silica gel gave 570 m g (44%) of the thietane 8 and 410 mg (31%) of the sulfide 9 ( N M R analysis of the crude mixture gave a ratio of 8 to 9 of I .5:l). The thietane after distillation ( I 50' (0.03 m m H g ) ) had ir (CC14) 3060, 3020, 2900, 2850, 1600, 1490, 1450, 1370, 700 cm-I; N M R (CCIj) 6 1.93 (s, 3 H), 2.50 (d, J = I O Hz, 1 H), 3.70 (d, J = 10 H z , I H ) ; ms, m/e 284 (M+). 252, 238, 166, 118. Anal. Calcd for ClsH24S: C , 80.24; H, 8.51; S, 11.25. Found: C , 80.25; H. 8.27; S. 1 1.26. The sulfide 9 was identified by comparison with an authentic specimen prepared as described below. It had ir (CC14) 3060, 3040,2850, 1620, 1490, 1450,900,700 cm-I; N M R (CC14) 6 3.00 (s, I H ) , 3.50 (s, 2 H), 5.20 (d. J = 2 Hz, 1 H ) , 5.40 (d, J = 2 Hz, I H): nis, m/e 284 (iM+), 166, 149, 135, 118. Anal. Calcd for Cl9H24S: C , 80.24; H, 8.51; S, 11.25. Found: C , 80.25; H , 8.27; S, I 1.26. Similarly, from n-trideuteriomethylstyrene6a the corresponding sulfide 15 and thietane 14 were obtained. The C-D stretch in 14 appeared at 2100 cm-', the terminal methylene in 15 at 900 cm-I. The ratio of 14 to 15 was 3:l ( N M R ) . A solution of the thione (100 mg, 0.6 mmol), a-methylstyrene (400 mg, 3.4 mmol). and a-trideuteriomethylstyrene in benzene (5 ml) was irradiated as described above. The sulfides 9 and 15, after distillation ( 1 55' (0.2 m m H g ) ) were subjected to mass spectroscopic analysis. The relative peak intensities at m/e 284, 285, 286, 287, 288 and 289 were 100, 22.0, 11.0, 52.3, 14.8, and 5.46 respectively. The peak at 285 ( M + I ) was entirely due to natural abundance isotopes (calcd 22.1%). Preparation of Sulfide 9. A solution of 504 mg (3.0 mmol) of ada m a n t y l t h i ~ lin ' ~ EtOH ( 1 5 ml) was added to an ice-cold solution of KOH (200 mg) in E t O H (5 ml). T o this mixture a t 5 "C was added, dropwise, a solution of 591 mg (3.0 mmol) of a-bromoethylstyreneb1 in E t O H (5 ml). After 15 min at 5' and 1 h at room temperature, the mixture was diluted with brine (60 ml) and the product isolated with ether. Distillation (0.03 mm) gave a fraction ( 145-150°) identical in every way with the material from the irradiation. Desulfurization of Thietane 8. A mixture of 210 mg (0.77 mol) of 8 and the catalyst (W-2) from I O g of Raney nickel alioy in benzene (50 ml) was refluxed for 12 h, the solution filtered (sintered glass-Celite), and the nickel washed with hot benzene (50 ml); the filtrate and washings were evaporated to give an oil (182 mg). G L C (6 ft X 0.25 in., 2.5% F F A P at 200') gave the spiran 10 (35 mg) and the olefin 11 (70 mg). The spiran had ir (CC14) 3040, 3020, 1600, 1490, 1445, 1375, 1100, 900 cm-I; N,VR (CCI?) 6 0.38 (d, J = 5 Hz, 1 H), 1.02 (d, J = 5 Hz, 1 H). 1.44 (s, 3 H ) . Anal. Calcd for C19H24:C , 90.41; H , 9.59. Found: C , 90.10, H, 9.70.
+
The olefin 11 had ir 3080, 3050, 3020, 1620, 1600, 1490, 1450, 1370, 900, 700 cm-I; N M R (CC14) 6 1.53 (s, 3 H), 4.78 (d, I H), 5.00 (d, I H ) ; ms, m/e 252, 237, 149. Anal. Calcd for C19H24: C , 90.41; H , 9.59. Found: C , 89.99; H , 9.65. Irradiation of Adamantanethione and 1,l'-Diphenylethylene. A solution of thione (570 mg, 3.4 mmol) and diphenylethylene (3.0 g, 16.7 mmol) in benzene (degassed by bubbling nitrogen for 30 min) (200 ml) was irradiated for 5 days. The product was chromatographed (silica gel) using petroleum ether (60-80°)-benzene, 19:1, to remove unchanged starting materials. T h e material eluted with ethyl acetate was separated by preparative T L C using first benzene-ethyl acetate (19:l) elution of the uv visible zone, and then using petroleum ether (60-80°)-benzene (4:l). The material 3a with RJ -0.4 was eluted and crystallized from ethanol, mp 128-130' (95 mg, 8%). It had ir (CC14) 3060, 1600. 1490, 1450, 705 cm-I; N M R (CC14) 3.55 (s, 2 H); ms. m/e 346, 314, 300, 188, 166. Anal. Calcd for C24H26S: C , 83.20; H , 7.56; S, 9.24. Found: C, 82.86; H , 7.61; S, 9.19. Irradiation of Adamantanethione and Ethyl Vinyl Ether. A solution of thione (863 mg, 5.2 mmol) and ethyl vinyl ether (7.2 g, 0.1 mol) in benzene (20 mi) was irradiated for 8 days. Bulb-to-bulb ( 120' (0.03 m m H g ) ) distillation of the residue gave the thietane 4a (890 mg, 72%). From the distillation residue TLC gave the dimer 2 (20 nig), mp 305-306'. The analytical specimen of the thietane 4a was prepared by chromatography over neutral alumina followed by bulb-to-bulb distillation. It had ir (CC14) 1450, 1370, 1335, 1185, 1125, 1090 cm-'; N M R (CC14) 6 1.20 (t, X3 part of ABX3, J ~ =x J B X = 7 Hz, OCH2CH3). 2.87 (dd, B part of ABX system, J B X = 8 Hz, J A B = 9 H z 1 H), 2.98 (dd, A part of ABX, J A X = 7.5 Hz, 1 H ) , 3.35 and 3.49 ( A B part of ABX3. JAB= 10 Hz, J A X = J B X = 7 Hz, O C H > C H 3 ) ,4.16 (dd, X part of ABX system, - C H > C H O E t - ) ; ms, m/e 238, 192, 166. Anal. Calcd for C14H220S: C , 70.55; H, 9.31; S, 13.43. Found: C , 70.81; H, 8.96; S, 13.43. Irradiation of Adamantanethione and Fumaronitrile. A solution of the thione (1.66 g I O mmol) and fumaronitrile (3g, 38.5 mmol) in benzene (200 ml) was irradiated (after degassing by bubbling nitrogen for 30 min) for 7 days. At the completion of the irradiation, G L C (7 ft X 0.25 in., 5% F F A P on Chromosorb P) showed a ratio of fumaronitrile to maleonitrile of 2.7: 1 . The olefin was removed by sublimation (SO' (0.03 mmHg)). Chromatography on silica gel ( 1 50 g of G F 254) using benzene as eluent gave thietane A , mp 105-106' (from ethanol, 650 mg) and thietane B, m p 145-146' (from ethanol, 630 mg). Thietane A had N M R (CDCI3) 6 4.07, 4.19 (AB, J = 5 Hz, - C H C N - C H ( C N ) S - ) ; ms, m/e 244, 173, 166. Anal. Calcd for C14HlhN2S: C , 68.83; H. 6.60; N , 11.47; S. 13.10.Found:C,69.10;H,6.84;N, 11.68;S,13.28. Thietane B had N M R (CDCIj) 6 4.25. 4.49 (AB, J = 9 Hz, - C H C N C H ( C N ) S - ) ; ms, m/e 244, 173, 166. Anal. Found: C , 69.05: H, 6.85; N, 11.61; S , 13.39. Irradiation of Adamantanethione and trsnsbtilbene. A solution of thione (650 mg, 3.9 mmol) and trans-stilbene (3.6 g, 20 mmol) in benzene (40 ml) was degassed and irradiated for I O days. The residue after removal of solvent was chromatographed over silica gel (BDH, 50 g, 60-200 mesh), eluting with petroleum ether (6080°, 600 ml) and petroleum ether-benzene (9:l. 300 ml). The material in the first 400 ml of petroleum ether elution contained stilbenes, thietanes 7, dimer, and unidentified material. The later elution contained mostly thietanes. The first fraction was distilled (120' (0.01 m m H g ) ) and the residue chromatographed to give the dimer (15 ing) and thietanes (310 mg). The latter was combined with the later fractions. N M R analysis indicated a mixture of thietanes of -I 5: I . Crystallization from ethanol gave one isomer (930 mg. 69%), mp 106.5-107.5'. It had N M R (CCI4) d 3.87, 4.76 (AB, J = Hz, -CH(C6H5)CH(C6H5)-S); ms, m/e 224, 180, 166. Anal. Calcd for C24H26S: C , 83.20; H , 7.56; S, 9.26. Found: C , 83.40; H. 7.68; S, 9.30. Determination of the Stationary State in the Stilbene Addition. Benzene solutions of thione (4 ml, 2 X lo-' M ) and trans-stilbene were degassed and irradiated ( A > 420 nm) for 3 days. After irradiation the solutions were analyzed by G L C (6.5 ft X 0.25 in., 2.5% F F A P on Chromosorb P, 180'). The results gave initial concentration of stilbene (cis/trans ratio): 0.4 M (8.3 I ) . 0. I M (8.20).
L a w r e n c e , Liao, de Mayo, R a m a m u r t h y
/
Thione P h o t o c h e m i s t r y
2226 0.06 M (8.31). Irradiation of Adamantanethione and Acrylonitrile. A solution o f 300 mg o f adamantanethione a n d 7.8 g o f a c r y l o n i t r i l e in 25 ml o f benzene was i r r a d i a t e d ( A > 420 n m ) t o the disappearance of the thione. T h e crude p r o d u c t m i x t u r e showed the f o r m a t i o n o f only one p r o d u c t (6 f t X 0 125 in 5% SE-30, 150' o r 6 ft X 0.25 in. 5% Carbowax. 170') a p a r t f r o m d i m e r 2. C h r o m a t o g r a p h y o f the m i x t u r e over silica gel (BDH 60-200 mesh) using petroleum etherbenzene (1:9) gave t h e thietane 5a (240 mg, 60%). T h e a n a l y t i c a l sample obtained b y preparative GLC ( 6 f t X 0.25 in., 5% Carbowax, 1 7 0 O ) of t h e b u l b - t o - b u l b distilled sample h a d ir (CC14) 2150, 1410, 1320, 1190, 1090. 955 c m - I : N M R (CDC13) 6 2.53 a n d 2.84 (AB p a r t o f ABX system, J4g = 10 H z , SCH2CHCN), 3.18 ( X p a r t o f ABX, J A X = 5 H z , J g x = 8.5 Hz, SCH2CHCN). ms, m/e 219, 173, 166: Precise mass 219.0999 (calcd 219.1081 j .
References and Notes Photochemical Synthesis. 63. This is part 20 in a series on Thione Photochemistry. Publication No. 149 from the Photochemistry Unit, University of Western Ontario. G. Oster, L. Citarel. and M. Goodman, J. Am. Chem. Soc.. 84, 703 (1962). E. T. Kaiser and T. F. Wulfers, J. Am. Chem. Soc.,86, 1897 (1964). K. Yamada, M. Yoshioka. and N. Sugiyama, J. Org. Chem., 33, 1240 (1968): Y. Omote, M. Yoshioka, K. Yamada, and N. Sugiyama, ibid., 32, 3676 (1967). G. Tsuchihashi, M. Yamauchi, and M. Fukuyama, Tetrahedron Lett., 1971 (1967); A. Ohno, N. Kito, and T. Koizumi, ibid.. 2421 (1971): A. Ohno. T. Koizumi, and Y. Ohnishi, Bull. Chem. Soc. Jpn., 44, 2511 (1971): N. Kito and A. Ohno, ibid., 46, 2487 (1973); Y. Ohnishi and A. Ohno, ibid., 46, 3868 (1973); N. Kit0 and A. Ohno, int. J. Su/fur Chem., 8, 427 (1973): A. Ohno, N. Kito, and N. Kawase, J. Polym. Sci.. Polym. Lett. Ed., 10, 133 (1972). A. Ohno, Y. Ohnishi, and G. Tsuchihashi, J. Am. Chem. Soc.,91, 5038 (1969), and papers there cited. M. lnatome and L. P. Kuhn, Tetrahedron Lett., 73 (1965). (a) H. Gotthardt, Chem. Ber., 105, 2008 (1972); (b) ibid., 107, 1856 (1974). H. J. T. Bos, H. Schinkel, and T. C. M. Wijsman, Tetrahedron Lett., 3905 (197 1). T. S.Cantrell, J. Org. Chem., 39, 853 (1974). R. S. H. Liu and V. Ramamurthy, Mol. Photochem., 3, 261 (1971). (a) D. R. Kemp and P. de Mayo. J. Chem. SOC.,Chem. Commun., 233, (1972): (b) P. de Mayo and A. A . Nicholson, isr. J. Chem., 10, 341 (1972): (c) R. Lapouyade and P. de Mayo, Can. J. Chem., 50, 4068 (1972): (d) D. S. L. Blackwell. P. de Mayo. and R. Suau. Tetrahedron Lett, 91 (1974) J R Bolton. K S Chen, A H Lawrence, and P de Mayo. J A m Chem Soc, 97, 1832 (1975) A preliminary account of part of this work has been reported: C. C. Liao and P. de Mayo, Chem. Commun., 1525 (1971). One or two reactions have been reported, but no mechanistic studies, e.g., D. S. L. Blackwell and P. de Mayo, J. Chem. Soc. Chem. Commun., 130 (1973); J. J. Worman, M. Shen, and P. C. Nichols, Can. J, Chem., 50, 3923 (1972). (a) P. de Mayo and H. Shizuka, J. Am. Chem. Soc., 95, 3942 (1973): (b) P. de Mayo and H. Shizuka, Mol. Photochem., 5 , 339 (1973): (c) P. de Mayo and R. Suau. J. Am. Chem. Soc., 96, 6807 (1974). S. 2. Levine, A. R. Knight, and R. P Steer, Chem. Phys. Lett., 29, 73 (1974); M. H. Hui, P. de Mayo, R. Suau, and W. R. Ware, ibid., 31, 257 (1975); J. R. Huber and M. Mahaney, ibid., 30, 410 (1975). J. W. Greidanus, Can. J. Chem., 48, 3530, 3593 (1970). (a) D. S. L. Blackwell, C. C. Liao, R. 0. Loutfy, P. de Mayo, and S. Paszyc, Mol. Photochem., 4, 171 (1972): (b) K. J. Rosengren. Acta Chem. Scand., 16, 2284 (1962): (c) see also C. A. Emeis and L. J. Oosterhoff, J. Chem. Phys., 54, 4809 (1971). The substances 4b and 5b were available from an alternative irradiation process; their properties will be described elsewhere." V. Ramamurthy and A. H. Lawrence, unpublished results. B. M. Trost. W. L. Schinski. F. Chen, and I. B. Mantz. J. Am. Chem. Soc., 93, 676 (1971): W. D. Keller, T. R. Luserbrink, and C. Sederholm, J. Chem. Phys., 44, 782 (1966). G. S. Hammond, J. Saltiel, A. A. Lamola, N. J. Turro, J. S.Bradshaw, D. 0. Cowan, R. C. Vogt, and J. C. Dalton, J, Am. Chem. Soc., 86, 3197 (1964); D. H. Valentine, Thesis, California Institute of Technology, 1966. C. A. Parker, "Photoluminescence in Solution", Elsevier. New York, N.Y., 1968, p 315. N. C. Baird and R . M. West, J. Am. Chem. Soc., 93, 4427 (1971); D. F. Evans, J. Chem. Soc., 1735 (1960). I. M. Hartmann, W. Hartmann, and G. 0.Schenk, Chem. Ber., 100, 3146 (1967): H. S. Case, M. J. S.Dewar, S. Kirschner. R. Pettit. and W. Siegeir. J. Am. Chem. Soc.,96, 7581 (1974).
Journal of the American Chemical Society
/ 98.8 / April
(28) A Schonberg and A. Stephenson, Ber., 668, 567 (1933): see also W. J. Middleton, E. G. Howard, and W. H. Sharkey, J. Org. Chem.. 30, 1375 (1965). (29) N. J. Turro and P. Wriede. J. Am. Chem. Soc., 92, 320 (1970). (30) N. J. Turro, C. Dalton, and P. Wriede. J. Am. Chem. Soc., 92, 1318 (1970); J. A. Barltrop and H. A. J. Carless, ibid., 94, 1951 (1972). (31) A. H. Lawrence and P. de Mayo, J. Am. Chem. SOC., 95,4084 (1973). (32) Michler's ketone, ET = 62.0 kcal/mol; @-acetonaphthone, ET = 59.4 kcal/mol; triphenylene, ET = 66.5 k c a V m 0 1 . ~The ~ singlet energies are also higher and kisc > 10" are required to avoid singlet transfer; this seems highly probable for the ketones. (33) S. Murov. "Handbook of Photochemistry", Marcel Dekker. New York, N.Y., 1973. (34) P.J. Wagner and I. Kochevar. J. Am. Chem. Soc., 90, 2232 (1968). (35) P. S. Engel and B. M. Monroe, Adv. Photochem., 8, 245 (1971). (36) The possibility that the low quantum efficiencies for these reactions is due to an inefficient generation of the responsible excited state is thus excluded. (37) Singlet quenching would be highly endothermic and can be excluded, especially in view of the very short thione singlet lifetime. (38) G. Porter and F. Wilkinson, Proc. R. Soc. London, Series A, 264, 1 (1961). (39) A. H. Lawrence, P. de Mayo, R. Bonneau, and J. Joussot-Dubien, Mol. Photochem., 5, 361 (1973). (40) H. J. L. Backstrom and K. Sandros, Acta Chem. Scand., 12, 823 (1958). (41) S. S. Collier, D. H. Slater, and J. G. Calvert. Photochem. Photobiol., 7, 737 (1968). (42) D. R. Arnold, Adv. Photochem., 6, 301 (1968). (43) Cf. inter alia among the earlier reports: E. J. Corey, J. D. Bass, R. LeMahieu, and R. B. Mitra. J. Am. Chem. SOC., 86, 5570 (1964); A. Cox, P. de Mayo, and R. W. Yip, ibid., 88, 1043 (1966). (44) Such is not the case with acetone which with electron-withdrawing substituents reacts only via the singlet in a stereospecific reaction having the reverse regiospecificity from that to be expected from the more stable biradical: N. J. Turro, P. Wriede, J. C. Dalton, D. R. Arnold, and A. Glick, J. Am. Chem. Soc., 89, 3951 (1967); see also ref 30. (45) (a) M. Feld, A. P. Stefani, and M. Szwarc, J. Am. Chem. SOC.,84, 4451 (1962); (b) A. B. Evnin, D. R. Arnold, L. A. Karnischky. and E. Strom, ibid., 92, 6082 (1970). (46) P.deMayo, Acc. Chem. Res., 4, 41 (1971). (47) J. L. Charlton, C. C. Liao, and P. de Mayo, J. Am. Chem. SOC., 93, 2463 (1971). (48) P. de Mayo and M. C. Usselman. An. R. Soc.ESP.Fis. Quim., Ser. B, 68, 779 (1972). (49) See, e.g., R. A. Caldwell, G. W. Sovocool, and R. P. Giajewski, J. Am. Chem. Soc., 95, 2549 (1973). Many of our arguments have been previously applied to oxetane formation by Wagner; see I. E. Kochevar and P. J. Wagner, J. Am. Chem. Soc., 94, 3859 (1972). (50) D. R. Rice and R. P. Steer, d Am. Chem. Soc., 96, 7364 (1974); R. P. Steer, private communication. See also, R. P. Steer, J. Chem. Soc., Chem. Commun., 106 (1973). See, however, M. C. Caserio and W. L. T. Novinson, J. Am. Chem. Soc., 92, 6082 (1970). (51) The differences between Steer's thietane and the dimer 2 with regard to steric interactions are not such as to lead us to expect that dimer A should favor the dissociative transoid conformation. (52) The bulk of the adamantyl would disfavor closure. However, in less sterically exacting situations the closure of such a biradical has already been proposed to explain (by the elimination of sulfur as HzS) the formation of ii from i:
U
I
(53) (54) (55) (56) (57)
(58) (59)
(60) (61)
N. Ishibe, M. Sunami, and M. Odani, Tetrahedron, 29, 2005 (1973); for a similar reaction see D. R. Kemp, A. H. Lawrence, C. C. Liao, R. 0. Loutfy, P. de Mayo, A. A. Nicholson, and S. Paszyc, Spec. Lect. lUPAC XXM, 367 (1971). A. Cox, D. R . Kemp. R. Lapouyade, P. de Mayo, R. Bonneau, and J. Joussot-Dubien. Can. J. Chem., in press. Species of this kind have been suggested as a possible intermediate in the quenching -"O exchange in excited acetone: N. C. Yang, W. Eisenhardt. and J. Libman. J. Am. Chem. Soc., 94, 4030 (1972). H. Beens and A. Weller, "Molecular Luminescence", E. C. Lim, Ed., W. A. Benjamin, New York, N.Y., 1969, p 203. From the equation = 0.89 IP 6.04: L. L. Miller, G. D. Nordblom. and E. A. Mayed. J. Org. Chem., 37, 916 (1972): cf. R. 0. Loutfy and R. 0. Loutfy. J. Phys. Chem., 77, 336 (1973). Taking IP as 8.1, it is assumed that thiofenchone has the same value as adamantanethione. Determinations of other bridged thiones in these laboratories suggest they are also of similar magnitude. See C. Guimon, D. Gonbeau, G. Pfister-Guillouzo, L. Asbrink, and J. Sandstrom. J. Hectron Spectrosc. Relat. Phenom. 4, 49 (1974). C. G. Hatchard and C. A. Parker, Proc. R. SOC.London. Ser. A, 235, 518 (1956). F. G. Moses, R. S. H. Liu. and B. M. Monroe, Mol. Photochem., 1, 245 (1969). W. F. Bayne, Ph.D. Thesis, University of Connecticut, 1970. H. Pines, H. Alul. and M. Kolobienski, J. Org. Chem., 22, 1113 (1957).
14, 1976
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